Tool for reducing spinal deformity

ABSTRACT

A tool for correcting abnormal curvatures of the spine is described. The tool includes a first member having a handle portion, a hose portion, with a neck portion connecting the handle portion to the hose portion. A second member likewise has a handle portion, and a hose portion with a neck portion connecting the handle portion to the hose portion. The two members are connected at the neck portions, wherein the hose portions include an open-sided elongated arm with a locking element to lock onto a vertebral clamp set, wherein the clamp set has a longitudinal rail attached to it after adjustment with the tool.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional application of U.S. patentapplication Ser. No. 09/633,480, filed on Aug. 7, 2000, now pending,priority of which is claimed under 35 U.S.C. § 120.

FIELD OF THE INVENTION

[0002] The present invention pertains to a tool for realigning anyabnormal curvature of the spine and more particularly to the tool usedwith posterior instrumentation having claw-like clamp sets to affix tovertebrae which enable reduction of the vertebrae followed by attachmentto a precontoured rail to reduce spinal deformities such as scoliosis.

BACKGROUND OF THE INVENTION

[0003] A normal spine when viewed from an anterior or posteriorperspective is longitudinally aligned with a straight vertical line. Thespine when viewed from either side presents a series of curvatures. Thetop curve in the neck or cervical spine has a convexity pointinganterior or towards the front. This type of curve (convexity pointinganterior) is called a lordotic curve. The next lower curve in the chestarea or thoracic spine has a convexity pointing posterior or towards theback. This type of curve (convexity pointing posterior) is called akyphotic curve. The lowest curve in the low back or lumbar area againhas a convexity pointing anteriorly.

[0004] Scoliosis is a deformity of the spinal column with threecomponents. The first is an apparent side bending of the spine whenviewed from the front or back (anterior/posterior or AP view). This is acoronal plane deformity. The second component is a loss of the normalkyphotic curvature in the thoracic or chest area when viewed from theside. This is a sagittal plane deformity. The third component is therotation of the spine around its own long axis. This is an axial planedeformity. This latter deformity can be appreciated on either a crosssectional x-ray study such as a CT scan (computerized axial tomographyscan) or more importantly from the rotation's effect on the attachedribs. It is this rotation that causes the characteristic “rib hump”which is the most disturbing element of the deformity to the patient andthe aspect of the deformity that is least well treated by currentsurgical treatment methods. Depending on the etiology of the spinaldeformity, one or more instances of abnormal curvature may be present inthe scoliotic spine and depending on the gravity of the deformity, thepreferred treatment may involve surgical procedures. In severe cases,bone fusion and instrumentation may be indicated. Instrumentation merelyserves to hold the vertebrae in their correct alignment while the bonefusion heals. Thus, in order to be effective, instrumentation must beable to correct vertebral alignment deformities in both the coronal andsagittal planes as well as correct for rotational aberrations.

[0005] Several procedures are available which include the use of eitheranterior or posterior instrumentation. Anterior and posteriorinstrumentation have their specific uses in different cases withattendant advantages and disadvantages. Posterior instrumentation isusually recommended for a typical deformity seen in patients which isknown as a right thoracic curvature. One benefit to posteriorinstrumentation is its relatively less invasive nature as compared withmost anterior methods.

[0006] Generally, posterior instrumentation involved the use of twolongitudinal rods secured to the spine by the use of multiple hooks,wires or sometimes screws and to each other with connecting plates. Thestandard method of spinal deformity reduction was to attach a pre-bent,pre-cut rod in the anticipated correction shape to the spine with aloose connection between the rod and hooks via several types of knownconnectors. The rod was then rotated inside the connectors into theimproved position. The connectors were then locked connecting the hooksecurely to the rod. A second rod was attached to the spine in a similarway with little if any correction obtainable at that time. Two plates orcross connectors were then attached to link the two rods together intoone effective unit.

[0007] This method had several disadvantages. First, this technique mosteffectively corrected the sagittal and coronal plane deformities but didlittle if anything for the axial deformity. Second, since each hook wasattached to its own respective single vertebra, all corrective force wasapplied to the vertebra in one location increasing the chance of hookcutout through the lamina. Third, since the rod was rotated with a looseconnection, there existed the possibility for the hook to dislodge fromthe lamina sometimes with catastrophic consequences for the patient'sspinal cord. Fourth, since a scoliotic deformity is an axial rotation ofa free body (the vertebra) without a fixed pivot, it requires twosimultaneous forces in opposite directions around an axis (a torque) tocorrect it. This concept was addressed in an earlier patent concerning atwo rod system. No current system provides this. Fifth, a two rod systemleaves the rods in a lateral position where the paraspinal muscles aresuppose to attach to the bone to help heal the spinal fusion. Sixth,since the rod is pre-bent and pre-cut to length before the correction isobtained and the rigidity of the patient's spine is variable and hard tomeasure preoperatively, the ultimate length and shape are determinedfrom an educated guess.

[0008] In view of the short comings of the existing procedures fortreating scoliotic spines, there is a need for improvements which allowthe use of a single-rod system that will reduce the scoliotic spine inall three planes, distribute the force during reduction over thevertebra, will attach rigidly to the spine before the reductionmaneuver, will apply a true derotation torque to correct the axial planedeformity, will leave the longitudinal rod in a more biologicallyadvantageous central place (where the spinous process was), and allowreduction of the deformity before cutting and contouring the rod.

SUMMARY OF THE INVENTION

[0009] The present invention relates to an apparatus and method forreducing a scoliotic spine. The apparatus includes at least onevertebral clamp set having a plurality of laminar hooks and a couplingmember for receiving a single central rail. The rail is cut andcontoured to a corrected alignment of the spine so that it can beattached to one or more clamp sets after reduction of the spine has beenperformed.

[0010] A preferred embodiment of the present invention includes fourclamp sets and a single rail, each clamp set has a transverse plate witha center region, and a first and second end. The first end has a pedicleextension to transmit force to a pedicle of a vertebra during reductionand the second end also has a pedicle extension to transmit force to apedicle during reduction of the vertebra when the force is applied inthe opposite direction. The plate has a first laminar hook to hook on asuperior portion of a first lamina of a vertebra. The first hook islocated on the first end of the plate and is integral with the plate.The plate has a second laminar hook to hook on an inferior portion of asecond lamina of a vertebra, such that the first and second hook are inopposed configuration, giving a claw-like hold on the vertebra. Thesecond hook is located on the second end of the plate and is madeadjustable with the plate to facilitate clamping and unclamping. Theplate also includes a rail coupling member having a slot to receive aprecontoured rail. The slot surface is configured to engage the railcross-sectional area and shape. The rail will preferably be multisidedhaving between 16 to 24 sides, and possibly as little as 4 to as many as120.

[0011] In another embodiment of the present invention, a clamp set forreducing spinal deformity is disclosed. The clamp set for affixing to avertebra has a transverse plate having a center region and a first and asecond end. The first end has a first pedicle extension, and the secondend has a second pedicle extension. At least one pedicle extension isused to transmit a downward force during reduction of the vertebra. Theclamp set also includes a first laminar hook located on the first end ofthe plate and is integral with the plate to hook on a superior portionof a first lamina of a vertebra. The clamp set also includes a secondlaminar hook to hook from an opposite direction on an inferior portionof a second lamina of the same vertebra. The second hook is adjustableto allow clamping and unclamping of the clamp set. The clamp setincludes a rail coupling member having a slot to receive a rail. Therail coupling member is located on the center region of the plate, andthe slot is configured to accept the rail cross-sectional area andshape.

[0012] In another embodiment of the present invention, a method forreducing the spine is disclosed. The method will include the steps of:attaching a plurality of vertebral clamp sets to vertebrae along theextent of the deformity of the spine, attaching reduction clamps to thevertebral clamps, attaching self-retaining arms to the reduction clampsin a loosened state, reducing the vertebra sequentially by grasping thereduction clamp and maneuvering it into an optimal position and theholding it there by securing the self retaining arm in a rigidcondition, then once the optimum position has been obtained, cutting andcontouring the rod to the reduced spine. The rail (rod) is then securedto the individual central connectors and the reduction clamps areremoved.

[0013] Many advantages are obtained with the use of posteriorinstrumentation constructed in accordance with the present invention.One advantage of a single rail system over a double rod system is that asingle rail causes less disruption of the healing muscles and allowsmore area for bone grafts. Another advantage is more secureinstrumentation attached to the individual vertebra as compared withsingular bone hooks which may shear from their lamina and cause damageto bone or nerve tissue. Another advantage is having a rail contoured tothe spine after reduction has taken place which avoids incorrect raillength and over-compensation or under-compensation of the rail contours.Another advantage is the use of a clamp set with pedicle extensionswhich distribute rotational forces downward onto the pedicle rather thansolely on the lamina during reduction of the vertebra, thus allowinggreater rotational forces without fear of damaging bone tissue orpopping hooks from their laminae. Another advantage is the use of amulti-sided rail which allows for fine adjustment of the degree ofreduction without slippage between the clamp sets and the rail, and thuscan eliminate the use of a two rod system and further provides greaterrotational stability.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing aspects and many of the attendant advantages ofthis invention will become more readily appreciated as the same becomebetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

[0015]FIG. 1 shows a top plan view of an embodiment of a clamp setconstructed in accordance with the present invention;

[0016]FIG. 2 shows a plan side view of an embodiment of FIG. 1 beingused in an apparatus constructed in accordance with the presentinvention;

[0017]FIG. 3 shows a perspective exploded view of the clamp set of FIG.1;

[0018]FIG. 4 shows an alternate embodiment for the clamp set of FIG. 1;

[0019]FIG. 5 shows a perspective view of a tool, constructed inaccordance with the present invention;

[0020]FIG. 6 shows a side plan view of the tool of FIG. 5; and

[0021]FIG. 7 shows a perspective view of an embodiment of a clamp setconstructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The present invention is directed to an apparatus and method forreducing the deformity of a scoliotic spine. The apparatus includes atleast one vertebral clamp set having a plurality of laminar hooks forclamping to a vertebra and a coupling member for receiving a rail. Therail is attached to the coupling member after the vertebra has beenreduced. Therefore, the rail is contoured to the corrected spinalcurvature before placement on the instrumentation.

[0023] Referring to FIG. 1, a component of the apparatus for reducingscoliosis is a clamp set 100 having a transverse plate 102 with a firstend 104, a second end 106, and a center region 108. In use, thetransverse plate 100 lies posteriorly of the vertebra 110. First 104 andsecond 106 ends are located lateral of the spinous process 112 (shown inphantom), while the center region 108 lies near the center of the baseof the spinous process 112 (shown in phantom). It should be understoodthat several anatomical parts of the vertebra may be removed to placethe clamp set 100 in its proper position.

[0024] The transverse plate 102 will generally define a planarrectangular body. However, the transverse plate 102 may be contoured tomatch the contours of the particular vertebra 110 to which it isattached. For example, the embodiment of FIG. 1 shows a transverse plate102 having angled surfaces along the length of the body to more closelyapproximate the contours of the posterior portion of vertebra 110.Located on the first end 104 of transverse plate 102 is a first hook114. A hook may be defined as any angled piece having ends facing insubstantially the same direction, so as to form a capture region onthree sides and one open side. In use, the first hook 114 fits over aportion of a first lamina 116, with the open side pointing in either thesuperior or anterior position depending on the particular situation. Aswith transverse plate 102, first hook 114 may have angled surfaces tomatch the contours of the vertebra 110.

[0025] As shown in FIG. 1, first hook 114 is continuous or integral withtransverse plate 102 and extending perpendicular to the long axis oftransverse plate 102. Attachment of first hook 114 to the transverseplate 102 may also be performed in any number of mechanically expedientways, such as bolting or welding the hook to the plate. Transverse plate102 is in a posterior position in relation to the vertebra 110, so firsthook 114 will proceed from transverse plate 102 in a superior direction(or inferior direction depending on the situation). First hook 114 willthen proceed anteriorly to an anterior part of first lamina 116, andthen proceed in an inferior direction so as to create a hook which hooksonto the first lamina 116 from the superior direction on three sides,the transverse plate 102 forming part of a side.

[0026] While one alternate embodiment of a hook has been described, itshould be readily apparent that hooks may take any number of forms,including arcuate, or cylindrical shapes or any combination thereof.While in one alternate embodiment, an integral hook is described, itshould be readily apparent that hooks which are attached by othermethods are also contemplated. For instance, a hook may be welded ontothe plate or held by attachment devices, such as bolts or screws.

[0027] Referring again to FIG. 1, a second hook 124 is located on thesecond end 106 of the transverse plate 102 and extends perpendicular tothe long axis of the plate 102. Second hook 102 is configured oppositeof the first hook 114, so as to hook on a second lamina 126 of the samevertebra 110 from an inferior direction. In the embodiment of FIG. 1,second hook 124 is attached to transverse plate 102 by the use of anadjustable device 128. Preferably, at least one hook is made adjustableor even detachable. Since first 114 and second 124 hook are in opposingor claw-like configuration, adjustability enables the attachment of theclamp set 100 to the vertebra 110 or allows its release. To enable theopposing claw-like holding action, second hook 124 will attach to thesecond lamina 126 from an opposite direction as the first hook 114.Second hook 124 will proceed from transverse plate 102 in an inferiordirection to an inferior part of the lamina 126. Second hook 124 willthen proceed anteriorly to the anterior part of the lamina 126, and thenproceed in a superior direction so as to hook onto the second lamina 126from the inferior direction on three sides with the transverse plate102. As with first hook 114, second hook may have angled surfaces tomatch the contours of the vertebra 110.

[0028] It is with reference to FIG. 3 that a description of theadjustable second hook 124 is next undertaken. It is intended that thealternate embodiment of FIG. 3 is meant to function in substantially thesame manner as the embodiment of FIG. 1. Furthermore, FIG. 3 shows oneof many alternates of FIG. 1 having modifications tailored for aparticular vertebra. It should also be understood that each vertebra ofa spinal column may be different, therefore necessitating modificationsto each of the clamp sets in the whole of the instrumentation apparatuswithout detracting from the functionality as described in thisspecification.

[0029] Second hook 124 may be detachable from transverse plate 102 ormay only be adjustable. Adjustability is minimally required tofacilitate placement and removal of the clamp set 100. In the embodimentof FIG. 3, second hook 124 is made detachable, and includes anattachment member 128 for securing second hook 124 to transverse plate102. Attachment member 128 is located on the second end 106 of thetransverse plate 102 lateral of the center region and centered on thelong axis of the plate 102. Attachment member 128 includes a bolt 136projecting from transverse plate 102 in a posterior direction when clampset 100 is in use. Bolt 136 has threads to engage corresponding nut 138.Nut 138 is used to snug the second hook 124 to the transverse plate 102in the manner described below. Second hook 124 is a curved piece havingtwo ends 144, 146 pointing substantially in the same direction. One end144 will be positioned posteriorly in relation to the second end 146. Onthe posterior end 144, second hook 124 has a notch 148, sized andconfigured to fit into the bolt 136 as the second hook 124 is slid fromthe side or top of the bolt 136. Posterior end portion 144 of secondhook 124 has first 150 and second 152 fingers that extend around bolt136 and create a pressure surface for nut 138 to snug against from theexterior surfaces. The nut 138 keeps second hook 124 securely held totransverse plate 102 when in use.

[0030] Although one embodiment has been described with respect to secondhook 124 and second hook attachment member 128, other alternativeembodiments of second hook 124 and attachment member 128 are possible.For example, the second hook may have an aperture rather than a notch tofit into the bolt. Further, it is possible for the bolt to reside on thehook and aperture or for the notch to reside on the transverse body.

[0031] While first and second vertebral securement devices have beendescribed as hooks, other vertebral securement devices may be employed.FIG. 7 shows an alternate of the vertebral securement devices. In theembodiment of FIG. 7, a plurality of pedicle screws may be used incooperation with the clamp set of the present invention. The pediclescrews are described in the inventor's previous U.S. Pat. Nos. 5,470,333and 5,127,912, which are herein incorporated by reference. FIG. 7 showsa clamp set 700, with a first pedicle screw 702 located on the first end704 of the clamp set 700 and a second pedicle screw 706 likewisecentrally located, but on the opposing second end 708 of the clamp set.The construction of the pedicle screws may take the form of any of thescrews in the aforementioned patents. Located on first 704 and second708 ends one is a countersunk bore 710 and 712, respectively, to acceptrounded head pedicle screws 702 and 706. Countersunk bores and roundedheads provide for pivoting of pedicle screws about a central axis toaccommodate varying vertebral anatomies.

[0032] Referring to FIG. 1, the clamp set 100 constructed in accordancewith the present invention includes a first 156 and a second 158 pedicleextension formed so as to extend over a portion of a first 160 andsecond 162 pedicle on the same vertebra. First pedicle extension 156 islocated on first end 104 of transverse plate 102 such that first pedicleextension 156 is continuous or integral with first end 104 of transverseplate 102. Pedicle extensions 156 and 158 function to transmit downwardforces on the pedicle during rotation of the vertebra, therefore pedicleextensions are deemed to be that part of transverse plate ends 104, 106which extend onto the pedicles of the vertebra. First pedicle extension156 is lateral of the center portion 108 of the transverse plate 102.Transverse plate 102 includes a second pedicle extension 158 formed soas to extend over a portion of a second pedicle 162 of the samevertebra. Second pedicle extension 158 is located on second end 106 oftransverse plate 102. Second pedicle extension 158 is continuous orintegral with second end 106 of transverse plate 102. Second pedicleextension 158 is lateral of the center region 108 of the transverseplate 102 and opposite with respect to the first pedicle extension 156.As shown in the embodiment of FIG. 1, first 156 and second 158 pedicleextensions are slightly angled relative to transverse plate 102, howeverother alternates of this embodiment may have more or less angledsurfaces or in some alternates be made to lie prone with no angledsurfaces such as shown in FIG. 3. It should be apparent that pedicleextensions are formed so as to transmit downward forces onto pedicleduring rotation, so in some alternates, the shape may take any of anumber of configurations to conform to the particular pedicle. First 156and second 158 pedicle extensions may also be shorter or longerdepending on the features of the individual vertebra. While first 156and second 158 pedicle extensions may be generally planar shaped pieces,first 156 and second 158 pedicle extensions may also be contoured toinclude curves to fit the anatomical features of the vertebra 110 andsome anatomical features of the vertebra may be removed in order toposition the first 156 and second 158 pedicle extensions over the first160 and second 162 pedicles of the vertebra. While the embodiment ofFIG. 3 may appear different, it should be readily apparent that theclamp set 100 of FIG. 3 is intended to function as the clamp set 100 ofFIG. 1.

[0033] Referring to FIG. 1, the clamp set 100 constructed in accordancewith the present invention includes a rail coupling member 164 locatedin the center region 108 of the transverse plate 102. In use, railcoupling member 164 will be positioned posteriorly with respect tovertebra 110. In the embodiment shown in FIG. 3, rail coupling member isa cylindrical threaded piece attached to the transverse plate 102 by anynumber of well-known methods, such as welding. The rail coupling memberof FIG. 3 is intended to be similar to the coupling member of FIG. 1.While one embodiment of a rail coupling member has been described, othercoupling members may have a horizontal slot or a nut which threads onthe inside of the cylindrical body of the coupling member. Othercoupling members may include two cylindrical bodies for attaching to twolongitudinal rails, or a coupling member with two slots or recesses formore than one rail. Rail coupling member 164 is slotted to receive alongitudinal rail 166. Inside surface of rail coupling member 164 isconfigured to engage with a portion of the longitudinal rail 166cross-sectional shape 170. Therefore, when cross-sectional shape 170 ofrail 166 is circular, slot surface will assume a semicircular shape toengage rail 166 on all but upper portion of rail 166. Rail couplingmember 164 is threaded to engage a nut 168. Nut 168 can be snuggedagainst upper portion of longitudinal rail 166 to keep rail 166 inposition on the clamp set 100, thus preventing movement of the clamp setand vertebra in relation to rail 166. In the embodiment shown in FIG. 3,longitudinal rail 166 may have a circular cross-sectional shape 170, butother embodiments may have different cross-sectional areas and shapes.

[0034]FIG. 4 shows the preferred embodiment of the clamp set 300 andlongitudinal rail 302 constructed in accordance with the presentinvention. Particularly shown is the rail 302 having a multisidedcross-sectional shape 304. The number of sides present in thecross-sectional shape may vary depending on the tolerance required inachieving the desired reduction of the spine. The cross-sectional shapemay have as little as 4 sides and as many as 120 sides, and mostpreferably, 16 to 24 sides. It should be readily apparent that thisembodiment of the clamp set is intended to function in substantially thesame manner as the embodiments described by FIGS. 1, 2 and 3, except foruse of the multi-sided rail.

[0035] When a multi-sided rail is used in cooperation with the clamp setof the present invention, the rail attachment member walls are slightlyangled outward to give a narrowing taper to the channel created therein.In this manner, the rail may be rotated within the channel, but when thenut is snugged against the rail, the nut presses the rail into thenarrower section of the channel and the rail is prevented from furtherrotation in the clamp set.

[0036] As shown in FIG. 1, the clamp set 100 also includes a pair ofnotches 172 located on the superior and inferior edges of the transverseplate 102. Notch 172 is located proximate to the center region 108 ofthe transverse plate 100. Superior notch 172 and inferior notch (notshown) provide suitable grasping elements for the tool of FIG. 5. Whilegrasping elements as shown include indentations, the function of servingas suitable grasping elements for a tool is also accomplished by havingprotrusions on the clamp set to match indentions in the tool. Any othersuitable configuration or combination of male and female elements may beused.

[0037] Referring now to FIG. 2, a preferred embodiment of the apparatusincorporating the clamp set of the present invention is shown. A portionof the thoracic region of the vertebral column having kyphotic curvatureis shown with the apparatus affixed to four levels of thoracic vertebraeafter reduction of the vertebral column has occurred. The preferredembodiment includes four clamp sets and a rail. While the apparatus asshown is affixed to adjacent vertebrae, most preferably, the clamp setsare affixed to alternate levels. For instance, a typical deformity isknown as a right thoracic curvature, for this case, the four clamp setswould attach to the fourth, sixth, tenth and twelfth vertebra,preferably skipping the apical vertebra. At least two clamps are used incooperation with a longitudinal rod, and at most seventeen, depending onthe severity of the deformity. A single clamp set may be used withoutthe longitudinal rail. Still another alternate is the use of a clamp setwith only a single vertebral device.

[0038] A first clamp set 200 for use in the embodiment of FIG. 2 may beeither of the alternate embodiments of FIGS. 1, 3, or 4. The clamp set200 includes a first 202 and a second 204 laminar hook in opposingconfiguration so as to clamp to a first vertebra 206 on a first 208 andsecond 210 lamina, respectively, of the first vertebra 206. It should bereadily understood that a vertebra of the thoracic region of the spinalcolumn inherently possesses a first and a second lamina as well as afirst and a second pedicle. The first 202 and second 204 laminar hooksattach to first 208 and second 210 laminae from a superior and inferiordirection, respectively. As can be perceived from FIG. 2, first 202 andsecond 204 laminar hooks surround the respective laminae 208 and 210,from three sides. The first clamp set 200 is posteriorly positioned inrelation to the first vertebra 206 such that rail coupling member 248 islikewise posteriorly positioned.

[0039] A second clamp set 212 of the instrumentation apparatus similarlyincludes a third 214 and a fourth 216 laminar hook in opposingconfiguration so as to clamp to a second vertebra 218 on a third 220 anda fourth 222 lamina, respectively, of the second vertebra 218. The third214 and fourth 216 laminar hooks attach to third 220 and fourth 222laminae from a superior and inferior direction, respectively. As can beperceived from FIG. 2, third 214 and fourth 216 laminar hooks surroundthe respective laminae 220 and 222 from three sides. The second clampset 212 is posteriorly positioned in relation to the second vertebra 218such that rail coupling member 250 is likewise posteriorly positioned.

[0040] A third clamp set 224 similarly includes a fifth 226 and a sixth228 laminar hook in opposing configuration so as to clamp to a thirdvertebra 230 on a fifth 232 and a sixth 234 lamina, respectively, of thethird vertebra 230. The fifth 226 and sixth 228 laminar hooks attach tofifth 232 and sixth 234 laminae from a superior and inferior direction,respectively. As can be perceived from FIG. 2, fifth 226 and sixth 228laminar hooks surround the respective laminae 232 and 234 from threesides. The third clamp set 224 is posteriorly positioned in relation tothe third vertebra 230, such that rail coupling member 252 is likewiseposteriorly positioned. A fourth clamp set 236 similarly includes aseventh 238 and an eighth 240 laminar hooks in opposing configuration soas to clamp to a fourth vertebra 242 on a seventh 244 and an eighth 246lamina of the fourth vertebra 242. The seventh 238 and eighth 240laminar hooks attach to a seventh 244 and an eighth 246 laminae from asuperior and inferior direction, respectively. As can be perceived fromFIG. 2, seventh 238 and eighth 240 laminar hooks surround the respectivelaminae 244 and 246 from three sides. The fourth clamp set 236 isposteriorly positioned in relation to the fourth vertebra 242, such thatrail coupling member 254 is likewise posteriorly positioned. Second 204,fourth 216, sixth 228 and eighth 240 laminar hooks are adjustable so asto enable placement of each clamp set on the respective vertebrae. Theadjustable hooks are held to the clamp set by a nut.

[0041] A longitudinal rail 256 contoured to the reduced configuration ofthe spine is attached to each of the respective clamp sets 200, 212, 224and 236 at the rail coupling member 248, 250, 252 and 254. The rail 256is held to the clamp sets by the use of a nut snugged against the rail256 at each rail coupling member 248, 250, 252 and 254. Each couplingmember projects posteriorly in a region formerly occupied by the spinousprocess such that the rail likewise occupies the region occupied by thespinous process. Only a single central rail is required in theinstrumentation constructed in accordance with the present invention. Inapplying the apparatus as described above, it should be readilyunderstood that several elements of the vertebral column may have toremoved in order to place the clamp sets and rail in the appropriateposition. Since the apparatus is located centrally on the spinal column,the paraspinal muscles are not interfered with.

[0042] Use of the apparatus in spinal reduction will now be describedwith reference to FIGS. 2 and 3. To begin placement of theinstrumentation on the spinal column, the apparatus must be in adisassembled state. As mentioned earlier, the preferred embodiment ofthis medical instrumentation will include four clamp sets 200, 212, 224and 236. However, any number of clamp sets may be used depending on theparticular situation of the patient. Therefore, description of the useof one clamp set will suffice to describe the use of the remainingthree. The first clamp set 200 will be attached to one level 206 of thevertebral column after the spinous process and other anatomical featuresof the vertebra have been modified or even removed to accommodate theclamp set. The first hook 202 of the first clamp set 200 is placed overthe first lamina 208 from a superior direction. Referring to FIG. 3, thefirst hook 114 being integral with the transverse plate 102 also placesthe transverse plate 102 on the posterior portion of the vertebra.Placement of the clamp set 200 on the vertebra 206 also locates railcoupling member 248 in the posterior configuration. First 156 and second158 pedicle extensions shown in FIG. 3 will be positioned on the firstand second pedicles of the vertebra such that first 156 and second 158pedicle extensions will lie opposite to each other and lateral to thecenter region of the clamp set.

[0043] Referring now to FIG. 2, second hook 204 is now placed on asecond lamina 210 from an inferior direction, such that first 202 andsecond 204 hook are in opposing configuration and provide a claw-likehold on the vertebra 206. Referring now to FIG. 3, second hook 148 mayeither slide into position around bolt 136, or second hook notch 148 mayslide into position from the top of the bolt 136. Second hook 204 ismade adjustable or detachable to facilitate placement on the secondlamina 210. Once second hook 204 is placed in position, nut 138 may besnugged against second hook 124 at first and second fingers 150 and 152at this time or may be loosely threaded for snugging at a later time. Inany event, nut 138 is preferably snugged prior to adjustment ofvertebra. Placement of the second 212, third 224 and fourth 226 clampsets may now proceed at this time in much the same manner as the firstclamp set 200. It should be readily apparent that the order of placementof the clamp sets on the vertebrae is of no consequence to thefunctioning of the apparatus. The advantages of the clamp set andapparatus should now be evident. The opposing hook configuration of thepresent invention provides a more reliable method of fastening posteriorinstrumentation to the spinal column than previously applied methods. Inaddition, the first 156 and second 158 pedicle extensions extend tocover all or part of the pedicles to transmit force downward on thepedicle during rotation of the vertebra. It should be readily apparentthat only one of the two pedicle extensions will see a transmittance offorce to the pedicle during rotation in any one direction. The pedicleextensions provide pressure distribution over a portion of the pedicle,decreasing the stress on the laminar hook, thus stronger rotationalforces may be applied without fear of damaging bone or nerve tissue.

[0044] Once each of the individual clamp sets has been attached to itsrespective vertebra, the superiormost 236 and inferiormost 200 clampsets are held in the neutral position, i.e., the vertebra attached tothese two clamp sets are not typically adjusted in the sagittal orcoronal planes, but can be rotated axially, then held in place while theremaining vertebrae are adjusted. These clamp sets prevent transferringa rotational force beyond the construct to the vertebrae that are notinstrumented (a problem known as crankshaft phenomena). Once thesuperiormost and inferiormost clamp sets are held in place, reduction ofthe remaining vertebrae can take place. In one procedure, a reductiontool is used to adjust the vertebra to achieve a more normal spinalconfiguration. A preferred reduction tool to be used in accordance withthe present invention has a first member with a handle portion, a noseportion, and a neck portion connecting the handle portion to the noseportion. A similar second member has a handle, neck, and nose portions.The first and second members are connected at the neck portions. Thereduction tool will be described below. Once reduction has beenperformed on an individual vertebra, or at any time thereafter, thereduction tool is held in place by the use of a robotic arm. The roboticarm clamps or grasps onto the reduction tool at a suitable location. Inone example, the tool is provided with a tab onto which the robotic armmay attach. Use of the tool and robotic arm maintains the vertebra inthe corrected state.

[0045] Once reduction of the indicated vertebrae has taken place, thelength and contour of the longitudinal rail 256 can be determined.Previous methods relied on having the rail contoured before reductionhad taken place, thus anticipating the amount of reduction that could beachieved. While this approach may have succeeded in a few instances,other times it was found that the rail was either too short or too longor the curvature of the rail was undercompensated or overcompensated.One advantage of the present invention is that it provides a morereliable method of achieving the proper length and shape and curvatureof a rail because the rail is measured, cut, and contoured to the properlength and shape after reduction has taken place.

[0046] The proper length and accurately contoured longitudinal rail 256can now be attached to each of the individual clamp sets 200, 212, 224and 236 in their reduced or neutral states at the respective couplingmembers 248, 250, 252 and 254. The longitudinal rail 256 fits into theslot of the rail coupling members and is snugged loosely with a nut ateach clamp set to prevent the rail from escaping the clamp set. Further,final adjustment of the clamp sets can take place because the slotallows rotation of the rail while inside the slot when the nut isloosely threaded. It is not necessary to use the longitudinal rail as aderotation device once it is set into the clamp sets because thedeformities have already been reduced. Whereas in previous methods,reduction took place by rotating a rod. This is where the big leap insafety between the method of the present invention and previous methodsis achieved. Once the adjustment of the clamp sets is complete, the nutsare snugged down on the rail to prevent rotation of the clamp sets. Inthe preferred embodiment, the rail 256 has multiple sides which engage asuitably configured portion of the coupling member slot surface, asshown in FIG. 4. The more sides the rail has, the finer the reductionadjustment that can be achieved. A multi-sided rail engages thecorresponding sides of the slot surface much like a hexagonal nutengaged in a wrench, thus a multi-sided longitudinal rail prevents anyrotational slippage of the clamp set which would cause the vertebra toslip back into its deformed state. This is the difference between thepresent invention and the two rod system. Two rods were previouslyrequired to act in unison to prevent rotation of the vertebra back tothe deformed condition. With a multi-sided nail, the rotational forcesare held in check by the interlocking surfaces of the rail and slot. Thenut, in this case, simply prevents the longitudinal rail releasing fromthe clamp set entirely and may only minimally relied upon to preventrotation of the clamp set relative to the rail. The longitudinal railholds the clamp sets in their reduced state and in relation to eachother, therefore the longitudinal rail must be of sturdy construction toresist bending by torsional forces.

[0047] In another aspect of the present invention, a tool is provided touse with the clamp set. FIG. 5 shows a tool 500 for adjusting anindividual clamp set 502. The tool of the present invention includes afirst arm member 504. The member 504 further includes a handle portion506, a neck portion 508, and a nose portion 510. The tool also includesa second arm member 512. The second member also includes a handleportion 514, a neck portion 516, and a nose portion 518. The first armmember 504 and the second arm member 512 are pivotally connected at theneck portions 508 and 516. The elongated handle portions 506 and 514allow for a multiplication of the gripping force at the relativelyshorter nose portions 510 and 518. A threaded rod 518 is locatedproximate to the outermost ends of the handle portions 506 and 514. Therod 518 traverses one of the handle portions and is threaded to asecurement nut 520 on the outside of the handle portion. Snugging on thenut 520 closes the handle portions 504 and 512 and applies the grippingforce to the clamp set 502. The tool also includes a rectangular tab522, for use during the spinal reduction method.

[0048] The nose portions 510 and 518 further include projections 524 and526 on the inside surfaces facing the clamp set 502. The projections aresuitably constructed so as to mate with the notches 528 on the traverseplate of the clamp set 502. Although projections on the nose portionshave been described, the present invention can suitably also utilizeindentations where the clamp set is provided with projections ratherthan notches. Further, any combination of mating parts may be utilizedin the present invention.

[0049] Referring now to FIG. 6, a feature of the tool 600 according tothe present invention is the ability to slide under the longitudinalrail 602 after the rail has been placed in the clamp set 604. As shownin FIG. 6, the nose portion 606 follows a curved line when viewededgewise which takes the gripping end 608 of the nose portion 606underneath the rail 602. In this manner, the tool 600 is first appliedto the clamp set 604, the tool is then held at the tab 608 to astabilizing arm (not shown). Next, the rail 602 is attached to the clampset 604 and finally the tool 600 is removed.

[0050] Referring now to FIG. 7, another embodiment of the clamp set 700according to the present invention includes pedicle screws 702 and 704to use as securement devices rather than laminar hooks. Pedicle screws702 and 704 traverse apertures 706 and 708 disposed in the body of theclamp set 700. Apertures 706 and 708 are countersunk so as to allowarticulation of the pedicle screws 702 and 704 within the apertures. Theclamp set 700 is meant to be similar in operation to the clamp setsshown in FIGS. 1, 3 and 4, in that the clamp set 700 has pedicleextensions to transmit downward rotational forces along the pedicle.

[0051] While the preferred embodiment of the invention has beenillustrated and described, it will be appreciated that various changescan be made therein without departing from the spirit and scope of theinvention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A tool for applying a force to a clamp set, comprising: a first member having a handle portion, a nose portion, and a neck portion connecting the handle portion to the nose portion, a second member having a handle portion, a nose portion, and a neck portion connecting the handle portion to the nose portion, and a pivotal connection securing the first member to the second member at the neck portions, wherein the nose portions include an open-sided elongated arm with a locking element to lock onto a vertebral clamp set, the clamp set having a longitudinal rail attached to it after adjustment of the clamp set with the tool.
 2. The tool of claim 1, further comprising a tab for attachment to a stabilizing arm.
 3. The tool of claim 2, wherein the nose portions further comprise a protrusion to mate with a corresponding notch on the clamp set. 